The present invention is directed to improvements of a product innovation referred to as a “self-leveling wheelbarrow,” and which are also described in the inventors' pending patent application, U.S. Ser. Nos. 10/769,989 and 60/443,961. The wheelbarrow incorporates self-adjusting legs which conform to the terrain and lock into place when at rest on the ground. The self-leveling feature offers added stability and provides a significant advantage over conventional wheelbarrows when used on sloping or uneven terrain.
Conventional wheelbarrows are well suited for use on smooth, level surfaces. Their ease of use, excellent mobility, and low cost have made them the material handling equipment of choice for moving small loads in the construction and landscaping industries. As a result of the great success of the conventional wheelbarrow, their basic design has remained essentially unchanged for many years.
However, due to its high center of gravity, fixed leg assembly, and the inherent instability of a tripod-style base, the use of a conventional wheelbarrow on uneven or sloped terrain is somewhat restricted. These factors result in a tendency to overturn if the legs are not resting on a level surface. When level ground cannot be found in close proximity to the working area the worker may be forced to park the wheelbarrow some distance away. The additional walking between the wheelbarrow and the working area during loading or unloading reduces worker productivity. When parked on uneven or sloping terrain, extra care must be taken to avoid overturning and potential injury to the user. Often a wedge or block is placed beneath one leg in order to provide additional stability and prevent overturning. These common problems associated with conventional wheelbarrows are illustrated in FIG. 1.
A simple solution has been devised which greatly improves the stability of a wheelbarrow on sloping or uneven ground and eliminates its tendency to overturn. A self-adjusting mechanism has been added to the leg assembly, allowing the legs to conform to the terrain as the wheelbarrow is lowered and locked into position when both legs are in contact with the resting surface. The self-leveling action increases stability and maintains the wheelbarrow in a level position. The center of gravity remains very nearly centered above the midpoint of the legs, thus the weight is more evenly distributed between the legs, and the tendency to overturn is diminished.
The present invention is directed to a self-leveling wheelbarrow comprising (a) a basin having a front end, a rear end, a left side and a right side; (b) a wheel disposed beneath the basin near said front end; (c) a handle assembly secured to the basin; and (d) a rear mounting bracket secured near the rear end of the basin, the mounting bracket having a top end secured beneath the basin. In certain aspects, the present invention further includes (a) a leg assembly comprising a pair of legs secured to one another by a centrally disposed plate, such that one of the pair of legs is positioned beneath the right side of the basin and the other one of the pair of legs is positioned beneath the left side of the basin, the plate further having a centrally disposed, arcuate top edge and a set of teeth arranged along the top edge; (b) a means for movably securing the leg assembly plate to the rear mounting bracket, such that the leg assembly may rotate in a counterclockwise or clockwise direction and in a vertical direction relative to the rear mounting bracket; and (c) a locking component secured beneath the basin and positioned above the top edge of the leg assembly plate, wherein the locking component is a C-channel member having a pair of adjacent side walls extending downward, each of the side walls further having a tapered edge; and whereby as the leg assembly contacts the underlying ground as the wheelbarrow is parked, the leg assembly rotates about the rear mounting bracket to accommodate the contour angle of the ground, sliding the top edge of the plate within the locking component to thereby engage the tapered edges of said locking component within adjacent teeth of the top edge of the leg assembly plate, thereby further locking the plate therein to prevent the leg assembly from rotating further, either in a clockwise direction of travel or a counterclockwise direction of travel. In certain embodiments, the locking component may be secured to the rear mounting bracket. In addition, each of the side walls of the locking component may include a notch, each notch further including the tapered edge for engagement between adjacent teeth of the top edge of the leg assembly plate when the locking component is engaged with the top edge of the leg assembly plate.
In addition to the basin, wheel, handle assembly, rear mounting bracket, and means for movably securing the leg assembly plate to the rear mounting bracket described above, other aspects of the present invention include (a) a first locking component secured to the leg assembly, the first locking component comprising an elongated inverted U-shaped member having two opposing ends, each of the ends secured to one of the rear legs, and a central portion disposed between the opposing ends; and (b) a second locking component secured beneath the basin and above the central portion of the first locking member, the second locking component comprising a first bar having a slot configured to engage therein the central portion of the first locking component. In operation, as the leg assembly contacts the underlying ground as the wheelbarrow is parked, the leg assembly rotates about the rear mounting bracket to accommodate the contour angle of the ground, sliding the central portion of the first locking component within the slot of the second locking component, thereby locking the central portion of the first locking component therein to prevent the leg assembly from rotating further, either in a clockwise direction of travel or a counterclockwise direction of travel. In other aspects of this embodiment, the second locking component may further include a second bar adjacent the first bar, the second bar having a slot configured to engage therein the central portion of the first locking component, with the slots of the first and second bars being in registration with one another. In addition, the second locking component may secured to the rear mounting bracket.
In addition to the basin, wheel, handle assembly, rear mounting bracket, and means for movably securing the leg assembly plate to the rear mounting bracket described above, other aspects of the present invention also include (a) a first locking component secured to the leg assembly, the first locking component comprising an inverted elongated U-shaped member having two opposing ends, each of the ends secured to one of the rear legs, and a central portion disposed between the opposing ends, the first locking component further including a series of holes penetrating through the first locking component; and (b) a second locking component secured beneath the basin above the first locking component, the second locking component comprising a locking pin configured for engagement within one of the holes of the first locking component. In operation, as the leg assembly contacts the underlying ground as the wheelbarrow is parked, the leg assembly rotates against the rear mounting bracket to accommodate the contour angle of the ground, sliding the central portion of the first locking component upwards for engagement of the locking pin within one of the holes, thereby locking the central portion of the first locking component therein to prevent the leg assembly from rotating, either in a clockwise direction of travel or a counterclockwise direction of travel. In other aspects of the present invention, the holes of the first locking component may be a series of rectangular shaped notches penetrating an outer edge of the first locking component, and wherein the locking pin is a rectangular tab configured for locking engagement within one of the notches. In this embodiment, as in the embodiments described above, the second locking component may be secured to the rear mounting bracket.
The means for movably securing the leg assembly plate to the rear mounting bracket may include a vertical slot provided in the rear mounting bracket and a pin extending from the leg assembly plate, the pin slidably engaged within the vertical slot to allow the leg assembly to move vertically within the slot and to rotate in a clockwise and counterclockwise direction about the pin. Alternatively, the means for movably securing the leg assembly plate to the rear mounting bracket may include a vertical slot provided in the leg assembly plate and a pin extending from the rear mounting bracket, the pin also engaged within the vertical slot of the leg assembly plate to allow for similar vertical and rotational movement of the leg assembly plate against the rear mounting bracket.